U.S. patent number 7,406,733 [Application Number 11/128,473] was granted by the patent office on 2008-08-05 for elastomeric fabric load bearing surface.
This patent grant is currently assigned to Illinois Tool Works Inc.. Invention is credited to Timothy P. Coffield, Daniel S. Sommerfeld, Joseph D. Ward.
United States Patent |
7,406,733 |
Coffield , et al. |
August 5, 2008 |
Elastomeric fabric load bearing surface
Abstract
An elastomeric fabric load bearing surface having a non-linear
force/deflection profile. In one embodiment, the load bearing
surface includes multiple layers, at least one of which is an
elastomeric fabric. The various layers cooperate with one another
to define a non-linear force/deflection profile. In one embodiment,
the load bearing surface includes an upper layer of elastomeric
fabric and a lower layer of elastomeric fabric, and the two layers
are stretched in different directions. In a second aspect, the load
bearing surface includes at least one layer of elastomeric fabric
that follows a non-linear pattern. In one embodiment of this second
aspect, the fabric defines a body-supporting surface and includes a
plurality of undulations away from the body-supporting surface.
Inventors: |
Coffield; Timothy P. (Grand
Rapids, MI), Sommerfeld; Daniel S. (Kalamazoo, MI), Ward;
Joseph D. (Grand Rapids, MI) |
Assignee: |
Illinois Tool Works Inc.
(Glenview, IL)
|
Family
ID: |
36954293 |
Appl.
No.: |
11/128,473 |
Filed: |
May 13, 2005 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20060255645 A1 |
Nov 16, 2006 |
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Current U.S.
Class: |
5/652.1; 5/653;
297/452.56; 297/452.15 |
Current CPC
Class: |
A47C
7/029 (20180801); A47C 7/282 (20130101) |
Current International
Class: |
A47C
7/02 (20060101) |
Field of
Search: |
;5/453,690,652.1,653,186.1 ;297/452.15,452.56 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Grosz; Alexander
Attorney, Agent or Firm: Warner Norcross & Judd LLP
Claims
The invention claimed is:
1. A load bearing surface for a body supporting application
comprising: a support structure; an elastomeric seating surface
secured to said support structure, said seating surface including
an initial contact portion being deflectable under a load in
accordance with a first deflection profile and a support portion
deflectable under a load in accordance with a second deflection
profile; and wherein at least one of said initial contact portion
and said support portion is an elastomeric fabric having a
plurality of elastomeric filaments extending in a first direction,
said elastomeric fabric mounted to said support structure in a
stretched condition wherein said elastomeric filaments are
stretched in said first direction, said support portion including a
plurality of undulations in said fabric extending in a second
direction different from said first direction, said initial contact
portion and said support portion cooperatively define an overall
deflection profile for the load bearing surface, whereby an
increasing number of said elastomeric filaments become engaged as a
load increasingly deflects said elastomeric fabric.
2. The load bearing surface of claim 1 wherein at least one of said
initial contact portion and said support portion includes at least
one localized variation in load bearing characteristics to provide
localized control over the deflection profile of the load bearing
surface.
3. A load bearing surface comprising: a support structure; an
elastomeric membrane including a plurality of elastomeric
filaments, said membrane secured to said support structure in a
stretched configuration over an opening permitting said elastomeric
membrane to deflect under a load, said elastomeric filaments being
stretched over said opening in a first direction, said membrane
generally extending along and defining a body-supporting surface,
said membrane including a plurality of undulations away from said
body-supporting surface, each of said undulations having a
longitudinal extent extending in said first direction, whereby said
plurality of elastomeric filaments becomes increasingly engaged as
a load increasingly deflects said membrane.
4. The load bearing surface of claim 3 wherein said elastomeric
membrane is further defined as an elastomeric fabric, each of said
undulations having a longitudinal extent extending substantially
across said elastomeric fabric in said first direction.
5. The load bearing surface of claim 4 wherein each of said
undulations includes a leading portion, a trailing portion and a
central portion, said central portion extending between said
leading portion and said trailing portion, said central portions of
said plurality of undulations generally defining said
body-supporting surface.
6. The load bearing surface of claim 3 wherein said elastomeric
membrane includes a first region and a second region, said first
region including a first number of undulations over a given
distance, said second region including a second number of
undulations over said given distance, said first number being
different from said second number.
7. The load bearing surface of claim 3 wherein each of said
undulations includes at least one characteristic pre-selected to
provide the load bearing surface with a desired deflection
profile.
8. A load bearing surface comprising: a support structure: an
elastomeric membrane secured to said support structure in a
stretched configuration over an opening permitting said elastomeric
membrane to deflect under a load, said membrane generally extending
along and defining a body-supporting surface, said membrane
including a plurality of undulations away from said body-supporting
surface, whereby said membrane becomes increasingly engaged as a
load increasingly deflects said membrane, wherein each of said
plurality of said undulations includes a depth, at least one of
said undulations having a greater depth than another of said
undulations.
9. A load bearing surface for a body supporting application
comprising: a support structure; an elastomeric membrane having a
plurality of elastomeric filaments, said membrane mounted to said
support structure with said elastomeric filaments in a stretched
condition, said elastomeric membrane including a plurality of
support portions cooperatively defining a body-supporting surface
and including a plurality of transitions portions extending away
from said body-supporting surface forming a plurality of
undulations, said undulations each having a longitudinal extent
extending substantially across said membrane, said longitudinal
extents of said transitions portions being generally parallel to
each other.
10. The load bearing surface of claim 9 wherein said elastomeric
membrane is further defined as an elastomeric fabric.
11. The load bearing surface of claim 10 wherein each of said
support portions are generally planar and at least a portion of
each of said transition portions generally extends at an angle to a
corresponding support portion of greater than about forty five
degrees.
12. The load bearing surface of claim 10 wherein at least one of a
characteristic of said elastomeric fabric, a characteristic of said
support portions and a characteristic of said transition portions
is varied for location to location along the load bearing surface
to provide localized control over a deflection profile of the load
bearing surface.
13. The load bearing surface of claim 9 wherein a shape of each of
said transition portions is selected to provide the load bearing
surface with a desired deflection profile.
14. The load bearing surface of claim 9 wherein a number of said
plurality of support portions is selected to provide the load
bearing surface with a desired deflection profile.
15. The load bearing surface of claim 9 wherein each of said
transition portions extends to a depth selected to provide the load
bearing surface with a desired deflection profile.
16. The load bearing surface of claim 9 wherein at least one of
said transition portions extends along a curve having a varying
radius of curvature, said varying radius of curvature selected to
provide the load bearing surface with a desired deflection profile.
Description
BACKGROUND OF THE INVENTION
The present invention relates to load bearing surfaces, and more
particularly to elastomeric fabric load bearing surfaces, such as
the seat or back of a chair or bench, or the support surface of a
bed, cot or other similar body-supporting product.
There is a continuing effort to develop new and improved load
bearing surfaces for use in body-supporting applications, such as
the support surfaces in seating, cots and beds. It is desirable for
load bearing surfaces to be, among other things, comfortable,
durable and relatively inexpensive to manufacture and assemble.
There is an increasing use of elastomeric load bearing fabrics in
the seating industry. For example, there are a variety of office
chairs available from well-known suppliers that include seat and
back portions manufactured from elastomeric fabric. In a
conventional application of this type, a layer of elastomeric
fabric is stretched across a frame over an opening. In use, the
elastomeric fabric elastically deflects to provide a resilient,
somewhat cushion-like response to a load. Elastomeric load bearing
fabrics are typically manufactured from a weave of elastomeric
monofilaments and multifilament yarns, but may include other woven
and non-woven constructions. For example, some elastomeric fabrics
are woven entirely from elastomeric monofilaments (i.e. the fill
yarns are replaced by elastomeric filaments). Elastomeric load
bearing fabrics provide a comfortable, elastic, ventilated surface.
Although elastomeric fabric surfaces can be quite comfortable in
many applications, they are not ideal in all body-support
applications. Conventional elastomeric fabric surfaces typically
deflect like a sling when a load is applied. Some ergonomists refer
to this type of deflection as "hammocking" and consider it
undesirable because it can cause the hips to rotate upward. This
rotation of the hips can cause discomfort, particularly over
extended periods. To minimize the degree of hammocking, many
elastomeric fabric surfaces are stretched even more tightly than
might otherwise be desired. Although this can reduce the amount of
deflection that occurs under load (and therefore reduce the degree
of hammocking), it can have an unintended negative impact on
comfort. More specifically, stretching the fabric tighter will
reduce the cushion-like feel of the surface making it feel more
like a tightly stretched drum.
Accordingly, there remains a need for an elastomeric fabric load
bearing surface that overcomes the limitation of existing
constructions.
SUMMARY OF THE INVENTION
The aforementioned problems are overcome by the present invention
which provides an elastomeric fabric load bearing surface with a
tunable, non-linear force/deflection profile. More particularly,
the present invention provides an elastomeric fabric load bearing
surface having a non-linear change in deflection in response to
increased loads.
In one embodiment, the present invention provides a multi-layer
load bearing surface in which the various layers cooperate to
define a non-linear force/deflection profile. In this embodiment,
the load bearing surface includes at least one layer of an
elastomeric fabric coupled with one or more additional support
layers. The additional support layers may also be elastomeric
fabric, but may alternatively be other load bearing materials, such
as elastomeric membranes or conventional fabrics. As a load is
increasingly applied to the first layer, the second and any
additional layers become increasingly engaged by the load. This
results in a surface that provides greater support in response to
greater deflection. The specific force/deflection profile of the
load bearing surface can be controlled by varying the number and
characteristics of the various layers.
In one embodiment, at least one of the various layers is provided
with different support characteristics in one or more specific
regions. This permits a high degree of regional control over the
overall profile of the load bearing surface. For example, in a
two-layer embodiment, the lower layer can define one or more
openings. The openings can be positioned to coincide with the
gluteal portions of the occupant's body, thereby reducing pressure
on the ischium bones and providing a more cushion-like feel to the
occupant. The number of layers, material selection and other
characteristics of the load bearing surface can be controlled to
provide the desired force/deflection profile.
In a second embodiment of the present invention, the load bearing
surface includes a load bearing fabric that is configured in a
non-linear pattern. For example, the fabric may follow a wave-like
pattern. As the load increasingly deflects the fabric, more and
more of the fabric becomes engaged by the load. As a result, the
fabric provides increasing support for greater loads in a
non-linear manner. The size, location, configuration and other
characteristics of the wave, as well as the characteristics of the
fabric can be varied to provide control over the profile of the
surface.
The present invention provides a comfortable, highly tunable
elastomeric fabric load bearing surface. The elastomeric fabric
load bearing surface is relatively inexpensive to manufacture, and
provides a light-weight surface that can be ventilated to inhibit
heat retention. The present invention provides a load bearing
surface having a non-linear force/deflection profile that can be
tuned to exhibit support characteristics that are particularly well
suited for use in seating applications. If desired, the load
bearing surface can be tuned to closely mimic the support
characteristics of conventional cushion sets. Further, if desired,
select regions of the load bearing surface can be varied to provide
localized control over the characteristics of the surface. For
example, in multilayer applications, one or more of the layers may
include openings to provide reduced pressure in select regions. As
another example, in applications with non-linear fabric, the
configuration of the fabric can be varied from region to region to
provide the regions with different load bearing
characteristics.
These and other objects, advantages, and features of the invention
will be readily understood and appreciated by reference to the
detailed description of the preferred embodiment and the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an elastomeric fabric load bearing
surface in accordance with one embodiment of the present
invention.
FIG. 2 a perspective view of the load bearing surface with the
lower layer removed.
FIG. 3 is a sectional view of the load bearing surface with the
lower layer removed taken along line 3-3 of FIG. 2
FIG. 4 a perspective view of the load bearing surface with the
upper layer removed.
FIG. 5 is a sectional view of the load bearing surface with the
upper layer removed taken along line 5-5 of FIG. 4.
FIG. 6 is a sectional view of the load bearing surface taken along
line 6-6 of FIG. 1.
FIG. 7 is a top plan view of the upper layer.
FIG. 8 is a top plan view of the lower layer.
FIG. 9 is a perspective view of a load bearing surface in
accordance with a second aspect of the present invention.
FIG. 10 is a side elevational view of the load bearing surface of
FIG. 9.
FIG. 11 is an enlarged side elevational of a portion of the load
bearing surface.
FIG. 12 is a sectional view of the load bearing surface taken along
line 12-12 of FIG. 10.
FIG. 13 is a side elevational view of an alternative load bearing
surface.
FIG. 14 is a side elevational view of a second alternative load
bearing surface.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A load bearing surface 10 according to one embodiment of the
present invention is shown in FIG. 1. The load bearing surface 10
shown in FIG. 1 is intended for use as a chair seat, and it
includes an upper layer 12 and a lower layer 14 that are suspended
from a chair seat frame 16. The frame 16 may in turn be mounted to
a chair pedestal (not shown). The upper layer 12 is stretched over
the lower layer 14 and is deflectable under a load. As the upper
layer 12 increasingly deflects under a load (not shown), the lower
layer 14 is increasingly engaged. As a result, the two layers 12
and 14 cooperate to define the overall force/deflection profile of
the load bearing surface 10. For purposes of disclosure, the
present invention is described in connection with various
alternative embodiments intended primarily for use in seating
applications. The present invention is not, however, limited to use
in seating applications, but may also be incorporated into other
load bearing applications. The support characteristics of the load
bearing surface 10 are highly adjustable, thereby permitting the
load bearing surface 10 to be tailored to support a variety of
loads in a variety of different applications.
As noted above, the load bearing surface 10 generally includes an
upper layer 12 (See FIG. 7) and a lower layer 14 (See FIG. 8) that
are secured to a frame 16. In this embodiment, the upper layer 12
of the load bearing surface 10 is manufactured from an elastomeric
fabric. Although the elastomeric fabric may be essentially any
woven or non-woven elastomeric fabric, the elastomeric fabric of
the illustrated embodiment includes elastomeric monofilaments woven
together with multifilament yarns or other fill yarns. In this
embodiment, the elastomeric monofilaments are manufactured from a
thermoplastic elastomer block copolymer. One suitable material of
this type is available from DuPont under the Hytrel.RTM. trademark.
The present invention is not, however, limited to any particular
elastomeric material and, to the contrary, may include essentially
any elastomeric filaments (monofilament or multifilament). As an
alternative to the use of fill yarn, the fabric may include
elastomeric filaments extending in both directions. If desired, the
warps and wefts of the elastomeric fabric may be welded together at
their intersections. The precise construction of the load bearing
fabric may vary from application to application depending in part
on the anticipated load and desired support characteristics. For
purposes of disclosure, the elastomeric fabric is illustrated in
the drawings with a weave that is unrealistically open for most
application. Although there may be applications where a weave that
is open to the illustrated degree is desired, the elastomeric
fabric will include a much tighter weave in typical
applications.
The lower layer 14 may be spaced apart from the upper layer 12, in
whole or in part, so that the spaced-apart region(s) do not
interact with the load until the upper layer 12 has deflected a
determined amount under load. Although the lower layer 14 may be an
elastomeric fabric, it may alternatively be other types of load
bearing materials. For example, the lower layer 14 may be a
non-elastomeric fabric, such as canvas, or an elastomeric membrane,
such as a molded elastomeric film. Although the illustrated
embodiment includes two layers, the number of layers may vary from
application to application. For example, the load bearing surface
10 may include a third layer (not shown) positioned below lower
layer 14 to allow further control over the force/deflection profile
of the load bearing surface once the third layer becomes engaged by
the load.
In the embodiment shown in FIGS. 1-8, the load bearing surface 10
is configured to function as the seat of a chair. In this
embodiment, the elastomeric fabric of the upper layer 12 is
stretched from side to side with respect to the seat frame 16.
FIGS. 2 and 3 are an illustration of the load bearing surface 10
with the lower layer 14 removed to show the general shape of the
upper layer 12 when stretched. In this embodiment, the left portion
40 and right portion 42 of the frame 16 are somewhat convex. As a
result of the convex shape of the left and right portions 40 and
42, stretching causes the upper layer 12 to follow a generally
convex shape, with a gradual curve extending from front to back. As
perhaps best seen in FIG. 3, the upper layer 12 is generally linear
in the direction of stretch (i.e. from left to right) despite the
curve in the front to back direction. In the embodiment of FIG. 1,
the lower layer 14 is, like the upper layer 12, an elastomeric
fabric. The lower layer 14 is stretched from front to back with
respect to the seat frame 16. FIGS. 4 and 5 show the load bearing
surface 10 with the upper layer 12 removed to highlight the
contours of the lower layer 14. In this embodiment, the front
portion 44 and back portion 46 of the frame 16 are somewhat
concave. As a result of the concave shape of the front and rear
portions 44 and 46, the stretched lower layer 14 follows a
generally concave shape, with a gradual curve extending from left
to right. When the upper layer 12 and lower layer 14 are combined,
the convex and concave profiles cooperate to provide significant
spacing between the two layers, particularly towards the center of
the seat (See FIG. 6).
The load bearing surface 10 resulting from the combination of upper
layer 12 and lower layer 14 provides a non-linear force/deflection
profile. More specifically, as a load is initially applied to the
surface, it engages only the upper layer 12. As the load increases
and the upper layer 12 deflects, it moves toward the lower layer
14. When the upper layer 12 deflects a sufficient amount, it comes
into engagement with the lower layer 14. Once this happens, the
upper layer 12 and lower layer 14 cooperate to support the load. As
a result of the additional support provided by the lower layer 14,
the overall support of the load bearing surface 10 increases in a
non-linear manner upon engagement of the lower layer 14. The
spacing between the upper layer 12 and lower layer 14 may be varied
to provide some control over the load required to engage the lower
layer 14. Further, the spacing may be varied in different regions
of the load bearing surface 10 to provide region control over the
force required to engage the lower layer 14.
If desired, one or more layers of the load bearing surface 10 can
be provided with regions of differing support. For example, in the
illustrated embodiment, the lower layer 14 defines a plurality of
openings 20, 22, 24 and 26. These openings are positioned on the
lower layer 14 to coincide with select pressure points, such as the
ischium bones. As a result, the support characteristics of the load
bearing surface 10 are different in these regions once the lower
layer 14 is engaged by the load. More specifically, these openings
20, 22, 24 and 26 provide the lower layer 14 with regions that
exhibit less resistance to deflection, relying essentially on the
upper layer 12 for support. Accordingly, they minimize pressure
points in the open regions. The number, size and location of the
openings may vary from application to application as desired to
tune the characteristics of the load bearing surface 10 to a
specific application. The support characteristics of any given
layer can be varied from region to region in alternative ways. For
example, in applications were the layer to be tuned is a sheet
material, the thickness of the sheet may be varied from region to
region or the sheet may be perforated in select regions. In
applications were the layer to be tuned is a fabric, examples
include varying the characteristics of the fabric strands from
region to region, stretching the fabric different amounts in
different regions, adding additional support strands in select
regions, welding the intersecting strands of the fabric together
only in select regions or, as noted above, by varying the spacing
of the layers in select regions.
The various layers 12 and 14 of the load bearing surface 10 can be
secured to a support structure in essentially any way capable of
supporting the intended loads. In the illustrated embodiment, the
load bearing surface 10 includes a frame 16 and a single carrier 18
for attaching the layers 12 and 14 to the frame 16. The frame 16 is
a relatively rigid component providing a majority of the structural
support for the seat. The frame 16 may be manufactured from
suitable structural plastics, for example, by injection molding.
The frame 16 may define a channel 30 to receive the carrier 18. The
carrier 18 of this embodiment provides a structure for securing the
layers 12 and 14 to the frame 16. During manufacture, the carrier
18 may be interconnected with the upper layer 12 and the lower
layer 14 and then the assembly may be connected to the frame 16.
For example, the carrier 18 may be connected to the frame 16 within
the channel 30 by fasteners, adhesives or through the use of slots
and locking tabs (not shown) built into the carrier 18 and frame
16. Alternatively, the two layers 12 and 14 may be attached to
separate carriers (not shown) and then each carrier (not shown) can
be separately secured to the frame 16.
The various layers 12 and 14 can be secured to the carrier 18 (or
carriers) in essentially any way capable of supporting the intended
loads. In one embodiment, the carrier 18 is molded in situ about
the two layers 12 and 14. In one specific example of this
construction, the two layers 12 and 14 are secured to the carrier
18 by pre-stretching the two layers 12 and 14 and then holding the
two layers 12 and 14 in the stretched state within the carrier mold
(not shown) while the carrier 18 is molded in situ onto the layers
12 and 14. U.S. Pat. No. 6,702,390 to Stumpf et al discloses
structure for performing a similar manufacturing process including
only a single layer of fabric. The apparatus of U.S. Pat. No.
6,702,390 can be readily modified for use with the present
invention by incorporating a second loom for holding the second
layer. U.S. Pat. No. 6,702,390 is incorporated by reference into
this application in its entirety. If desired, a separate carrier
may be molded to each layer so that each layer may be separately
attached to the frame.
Alternatively, the carrier 18 can be molded in situ about two
layers 12 and 14 when the two layers are in a relaxed state. In
this embodiment, the carrier 18 may be manufactured from a
stretchable material that permits the carrier 18 and the layers 12
and 14 to be stretched together. The stretched assembly of carrier
18 and layers 12 and 14 may be attached to the frame 16, which
retains the assembly in the stretched condition. U.S. Pat. No.
6,540,950 to Coffield discloses an attachment structure of this
type and is incorporated by reference into this application in its
entirety. In applications where the two layers 12 and 14 are to be
subject to the same stretch, a single carrier 18 can be
simultaneously molded to both layers 12 and 14. In applications
where each layer 12 and 14 is to be subjected to a different
stretch (e.g. stretched in different directions and/or stretched to
different amounts), separate carriers (not shown) can be molded to
each layer 12 and 14, and the two carriers can be separately
stretched and attached to the frame 16.
In another alternative, the attachment construction may include a
single carrier 18 having two halves that are closed about the
layers 12 and 14 to hold them in place. An attachment construction
of this type is shown in U.S. Pat. No. 6,511,562 to Coffield, which
is incorporated by reference into this application in its entirety.
If there is a desire to space the layers 12 and 14 apart from one
another along the edges, the carrier may include one or more
additional parts (not shown) positioned between the layers 12 and
14. For example, if it is desirable to space two layers, the
carrier may include a third part corresponding in overall shape
with the two carrier halves. This third part may be positioned
between the layers 12 and 14 and between the two carrier halves.
The various carrier parts and layers may be interconnected by
fasteners, such as screws, or by adhesives, such as cement.
In another alternative, the carrier(s) can be eliminated and the
layers can be directly attached to the support structure (e.g.
frame 16). For example, the frame 16 can be molded in situ directly
onto the upper and lower layers 12 and 14. As another example, the
frame 16 may include two halves that clamp about the edges of the
layers 12 and 14. If desired, additional frame parts (not shown)
may be sandwiched between the various layers to provide spacing
between the layers. The present invention is not limited to
applications in which the layers 12 and 14 are secured to a single
frame 16. Rather, the load bearing surface 10 may be supported on
multiple frames, for example, by incorporating a separate frame for
each layer.
Another embodiment in accordance with a second aspect of the
present invention is show in FIG. 9. In this embodiment, the
present invention includes a load bearing surface 100 having an
elastomeric fabric 102 that is stretched over an opening and is
configured to follow a non-linear pattern. The non-linear pattern
is configured to provide the load bearing surface 100 with a
controlled, non-linear force/deflection profile. More specifically,
the fabric 102 follows a pattern of undulations 110 that provide
the load bearing surface with depth in the direction of deflection.
Operation of the load bearing surface 100 is described in
connection with FIGS. 11 and 12. FIG. 11 shows the undulations 110
in the unloaded state in solid lines and shows the deflection of
the undulations 110 under increasing loads in phantom lines A, B
and C. As the load sinks deeper into the undulations 110, it
engages an increasingly greater number of fabric strands or
filaments. For example, FIG. 12 includes a lines D, E and F that
show varying degrees of deflection in an undulation 110. When the
fabric 102 deflects from its unloaded position to line D, the load
becomes engaged by each of the horizontally extending strands
disposed between the relaxed position and line D. Similarly,
additional deflection, for example, from line D to line E or line F
results in the engagement of even more horizontal strands. As the
number of engaged strands increases, the overall stiffness of the
load bearing surface increases. Accordingly, the load bearing
surface 100 becomes increasingly stiffer as the occupant sits
deeper in seat. In this way, the load bearing surface 110 has the
ability to automatically adjust its stiffness to varying loads.
The load bearing surface 100 of the illustrated embodiment is
intended for use as a seat for a chair (not shown). As shown, this
particular embodiment includes four largely identical undulations
110 that run parallel to one another and are intended to run from
left to right in the assembled chair. In this embodiment, the
fabric 102 is stretched in a direction that is coincident with the
longitudinal extent of the undulations 110. The degree of stretch
applied to the fabric 102 may vary from application to application
to provide the desired load bearing characteristics. In this
embodiment, the fabric 102 follows a repeating wave-like pattern in
which each undulation 110 of the fabric 102 includes angled leading
and trailing portions, 112 and 114 respectively, (collectively
referred to as transition portions) that are joined by a generally
planar central portion 116 (or support portion) (See FIGS. 10 and
11). The central portions 116 of the various undulations 110
cooperatively define a body-supporting surface in the sense that
they together define the general extent and shape of the load
bearing surface 100 before a load is applied. The body-supporting
surface may be planar or may be a curved surface, as desired. For
example, the fabric 102 may include central portions 116 that
follow a shape corresponding with that of the intended load. The
transition portions 112 and 114 extend away from the
body-supporting surface so that they become increasingly engaged
with the load as the fabric 102 undergoes greater deflection.
Although described in connection with a seating application, the
present invention is not limited to seating applications, but is
well-suited and readily adapted for use in other body-support
applications, such as the support surface in a chair back, cot or
bed.
The elastomeric fabric 102 may be mounted to a support structure in
essentially any manner. In the embodiment of FIGS. 9-14, the load
bearing surface 100 includes a caffier 108 that is interconnected
with the fabric 102. The caffier 108 may in turn be mounted to a
frame, such as the frame 16 shown in connection with the first
embodiment, or other support structure, such as the pedestal of a
chair (not shown). The carrier 108 may include multiple segments
that are affixed to opposite edges of the fabric 102, such as the
two segments 108a and 108b shown in FIG. 9. Alternatively, the
caffier 108 may extend continuously around the entire periphery of
the fabric 102. In applications with a split carrier, the carrier
segments 108a and 108b may be mounted to a single support structure
or to separate support structures that hold the two segments 108a
and 108b apart at the desired tension. As perhaps best shown in
FIGS. 10 and 11, the fabric 102 may be secured to the caffier 108a
in a wave-like configuration. This construction may be achieved in
a variety of different ways. For example, the fabric 102 may be
held in the desired wavy configuration within a mold cavity (not
shown) while the carrier segments 108a and 108b are molded in place
directly onto the fabric 102. As an alternative example, the
caffier segments 108a and 108b may each include upper and lower
segment halves that close on opposite sides of the fabric 106 to
hold it the desired wave-like pattern. If desired, the carrier 108
may be eliminated and the fabric 106 may be mounted directly to the
frame or other support structure using essentially any one of the
aforementioned attachment structures.
The number, size, shape and configuration of the undulations in the
fabric can be selected to provide control over the force and
deflection profile of the load bearing surface. These changes can
be uniformly implemented over the entire load bearing surface or
may be varied from one region to another across the surface to
provide localized control over the support characteristics of the
surface. For example, the undulations 110' in the fabric 102' may
vary in depth (or height) as necessary to accommodate the desired
range of loads, as shown in FIG. 14. In this embodiment, the
undulations 110' increase in depth toward the center of the load
bearing surface 100'. This embodiment is intended for use in
applications where the anticipated load increases toward the center
of the load bearing surface 110.' The undulations 110' with a
smaller depth require less fabric and therefore may decrease the
overall cost of the load bearing surface 100'. The support
characteristics of the load bearing surface may also be tuned by
varying the number of undulations over a given distance. Referring
again to FIG. 14, the number of undulations 110' is twice that
disclosed in the embodiment of FIG. 9. This increase in undulations
110' will result in a generally stiffer surface because there are a
greater number of transition portions 112' and 114' to support the
load. FIG. 13 shows an alternative embodiment in which the number
of undulations varies from one region to another across the load
bearing surface 100''. In this embodiment, there are a greater
number of undulations 110'' in the center of the load bearing
surface 100'' than in the front and back. As a result, the center
of the load bearing surface 100'' will provide a stiffer response
to a load. Further, the rate at which the load bearing surface
stiffens under load can be controlled by varying the angle of the
leading and trailing edges of each undulation. For example, it may
be desirable to lessen the angle of the transitions portions in the
front and rear regions of the load bearing surface to provide
differences in the stiffness between the front, read and central
regions. Referring now to FIG. 13, the transition portions 112''
and 114'' of each undulation may be curved (as exemplified by
transition portion 148) or linear (as exemplified by transition
portion 150, which is shown in broken lines). Although the
transition portions 112'' and 114'' shown in solid lines are
somewhat convex, the transition portions may alternatively be
concave, as exemplified by transition portion 156, which is shown
in broken lines. The specific curve of the transition portions
112'' and 114'' can be engineered to provide a high degree of
control over the rate at which the seat stiffens. For example, the
radius of curvature may vary over the transition portion 112'' and
114'' to vary the stiffness at different depths. In some
applications, it may be desirable for the transition portions to
extend at a negative angle such that the central portion overlaps
the transition portions. This is exemplified by transition portion
154, which is shown in broken lines. A negative angle will result
in the central portion 116'' and transition portion 112'' or 114''
being in an overlapping relationship with respect to the direction
of deflection. This can provide an even greater increase in
stiffness once the overlapping portions become engaged to
cooperatively support the load.
Although this second aspect of the present invention is described
in connection with elastomeric fabrics, it may also be implemented
with other types of elastomeric membranes, such as elastomeric
films. A wide variety of elastomeric materials are suitable for
forming alternative elastomeric membranes. These membranes may be
molded, cast, extruded or otherwise formed using conventional
techniques and apparatus.
The present invention is illustrated in connection with load
bearing surfaces intended to extend in a substantially horizontal
orientation. The present invention may, however, be incorporated
into load bearing surfaces extending at other orientations. For
example, the present invention is well-suited for use in vertically
extending applications, such as a chair back.
The above description is that of various embodiments of the
invention. Various alterations and changes can be made without
departing from the spirit and broader aspects of the invention as
defined in the appended claims, which are to be interpreted in
accordance with the principles of patent law including the doctrine
of equivalents. Any reference to claim elements in the singular,
for example, using the articles "a," "an," "the" or "said," is not
to be construed as limiting the element to the singular.
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